Bug Description

As the summary says: Making a circle produces a Path, not a Circle element
Additionally it puts a bunch of duplicate proprietary Sodipodi properties (type;cx;cy;rx;ry) which wouldn't be necessary if it used Circle. Any reason to keep these legacy properties? Else convert them to "Inkscape".

The main difficulty is that a lot of Inkscape (and, indeed, SVG) features don't work on circles or ellipses, only paths. The best solution would be to use an ellipse or circle when possible, and automatically switch to using a path when some feature that requires a path is used.

That's what I had in mind. What, apart from the arcs, doesn't work on circles or ellipses?
If you perform path operations on two objects, obviously the result is a path. Currently I can use a circle element in a compound operation, like combine, which turns the circle into a path, punching a hole in another shape. I doubt that circle could be made back into a Circle element if broken apart, but what would be neat is if you've made an arc, and you have your Sodipodi attributes, if you close the arc again, it can be made back into a circle or ellipse element.

The first thing that comes to mind is text-on-path, which was the reason
we started creating circles/ellipses as paths in the first place (being
able to put text on a circle was a popular request). There's also SVG
markers, and anything having to do with path nodes generally ... it
might actually be easier (and shorter) to list the SVG shape-related
features that *do* work with circles and ellipses, rather than listing
all the ones that don't. The features that *do* work are: